This application claims the benefit of Korean Patent Application No. 2002-7029, filed Feb. 7, 2002, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an electrophotographic image forming apparatus, and more particularly, to a developer unit of an electrophotographic image forming apparatus whose structure is improved so as to prevent a wrap-around phenomenon of a developing solution occurring at both ends of a developer roller.
2. Description of the Related Art
An electrophotographic apparatus generally forms a latent electrostatic image on a photosensitive material, such as a photosensitive belt or a photosensitive drum, develops the latent electrostatic image into a visible toner image with toner having a predetermined color, and transfers the visible toner image to a sheet of paper to form a predetermined image.
The electrophotographic apparatus includes a developer unit, a transfer unit, and a fusing unit. The developer unit supplies toner to the photosensitive material to develop a latent electrostatic image formed thereon by a laser scanning unit into the visible toner image. The developer unit includes a developer roller, a deposit roller, and a metering blade. The developer roller is partially dipped into a developer contained in a developer container, is installed to rotate to be in contact with the photosensitive material, and supplies the developer to the photosensitive material. The deposit roller is dipped into the developer and deposits the developer on the developer roller using a difference in potential between the deposit roller and the developer roller. The metering blade controls a thickness of the developer that is attached onto the developer roller by the deposit roller.
The transfer unit is installed to rotate to be in contact with the photosensitive material. The transfer unit transfers the developed visible toner image formed on the photosensitive material to the paper disposed in a gap between the transfer unit and the photosensitive material.
The fusing unit fuses and fixes the transferred image on the paper by applying predetermined heat and pressure. The transfer unit may include a heat source so as to perform not only a transferring function but also a fusing and fixing function.
A paper supplying unit is installed to pick up the paper stacked in a cassette and supply the paper to the gap between the transfer unit and the photosensitive material. A paper discharging unit is installed to discharge the paper through the transfer unit and the fusing unit.
The metering blade is installed so as to contact the developer roller in a longitudinal direction of the developer roller and scrapes the developer to control the thickness of the developer that adheres to the surface of the developer roller by the deposit roller. Here, a portion of the developer scraped by the metering blade may leak out through both ends of the metering blade to the adjacent developer roller, which is called a xe2x80x9cwrap-around phenomenon.xe2x80x9d The leaking developer may flow to the photosensitive material that contacts the developer roller and to the toner image formed on the photosensitive material. This may cause a cross contamination of the developer in color printing.
Accordingly, in the prior art, sponges having a low hardness are attached to both ends of the metering blade so as to prevent the wrap-around phenomenon of the developer.
However, it is difficult to attach sponges having the low hardness to the metering blade and to install the metering blade so as to attach precisely the sponges to the metering blade. Further, the sponges are worn out as time goes by, and thus the developer leaks out through both ends of the metering blade.
To solve the above and other problems, it is an object of the present invention to provide a developer unit of an electrophotographic image forming apparatus whose structure is improved so as to prevent a developer from wrapping around both ends of a developer roller.
Additional objects and advantageous of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Accordingly, to achieve the above and other objects, there is provided a developer unit of an electrophotographic image forming apparatus. The developer unit includes a developer roller, a metering blade, and a blocking blade. The developer roller is installed to be partially dipped into a developer container and to rotate to supply a developer to a latent electrostatic image formed on a photosensitive material. The metering blade is installed to contact an outer circumference of the developer roller so as to control the developer attached to the outer circumference of the developer roller to a predetermined thickness. The blocking blade is installed between the developer roller and the metering blade to prevent a wrap-around phenomenon of the developer.